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Efficient enhancement of the accuracy of ray tracing
, Article 2010 IEEE International Symposium on Antennas and Propagation and CNC-USNC/URSI Radio Science Meeting - Leading the Wave, AP-S/URSI 2010, 11 July 2010 through 17 July 2010 ; July , 2010 ; 9781424449682 (ISBN) ; Parsa, S ; Shishegar, A. A ; Sharif University of Technology
2010
Abstract
Proper design of wireless personal and local area networks requires accurate characterization of radio wave propagation in indoor environments. The Shooting-and-Bouncing-Ray tracing (SBR) method, which uses Geometrical Optics (GO) approximation, has been widely used for indoor propagation modeling [1-2]
Proper Closed-form Representation for Site-specific Radio-wave Propagation
, Ph.D. Dissertation Sharif University of Technology ; Shishegar, Amir Ahmad (Supervisor)
Abstract
In this dissertation, a proper closed-form representation has been presented for the site specific indoor radio-wave propagation. Characteristic Green’s function (CGF) technique is used to obtain the integral representation of the Green’s function of a rectangular 2D room with dielectric slab walls. Based on numerical simulations, this method provide quite accurate results for wave propagation in the interior region (away from the walls) but the error increases for source or field points near the walls. The presented integral form of Green’s function has slow convergence and computed using Real images, complex images and rational function fitting methods. An error of less than 20 percent is...
Investigation and Representation of Practical Methods in Order to Scale Removal in Exchanger 4132 in the Urea Unit of Petrochemical Khorasan
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fatollah (Supervisor)
Abstract
In this research, utilizing the concepts of thermohydraulics theory, optimization of cost due to the scale formation in heat exchangers 4131 and 4132 in Khorasan petrochemical Co. urea unit. The objective function involves the minimization of the energy consumption and production losses. First, via ASPEN we simulated shortcuts of exchangers in order to examine the effects of temperature and velocity on the scale formation. The project optimization was done by GAMS and due to the presence of nonlinear terms in the scale rate equations using CONOPT solver. Eventually, modern practical methods were used with the purpose of reduction and eradication of the heat exchanger's scale formation. The...
Extraction of GLR detector for target lines in the range-time space of a search RADAR
, Article 2011 Microwaves, Radar and Remote Sensing Symposium, MRRS-2011 - Proceedings, 25 August 2011 through 27 August 2011, Kiev ; 2011 , Pages 336-339 ; 9781424496440 (ISBN) ; Moqiseh, A ; Nayebi, M. M ; Sharif University of Technology
2011
Abstract
In this paper, the disadvantages of using the Hough transform as a detector have been considered in a search radar. To illustrate the effect of these disadvantages on the performance of the detector, its performance has been compared with the optimum detectors. To do this, the Generalized Likelihood Ratio detector has been extracted for detecting a target line with unknown normal parameter pair in the search environment. Then, the performance of this detector has been compared with the Hough detector by extracting their Receiver Operation Characteristics. The results of this comparison, which has been done through simulations, show that the Generalized Likelihood Ratio detector has a better...
A New Algorithm for Multiple RF Sources Localization by Means of a Group of Robots
, M.Sc. Thesis Sharif University of Technology ; Bagheri Shouraki, Saeed (Supervisor)
Abstract
The main subject of this project is to present a new algorithm for multiple RF sources localization by means of a group of robots. This problem (locating multiple radio sources) could be utilized in many domains, either military (passive radars) or civil (search and rescue) uses. Confronting detrimental effects of real environment on wave’s propagation pattern is the main challenge in this problem. Optimized movement of robots has been chosen as basic strategy to overcome this challenge. Presenting a general solution for this problem requires researches in four topics. The first one is simulation of environment and sensor with main objective of evaluating obtained algorithms’ performance....
Theory of Nonlinear Lumped Element Transmission Lines
, M.Sc. Thesis Sharif University of Technology ; Farzaneh, Forouhar (Supervisor) ; Hashemi, Morad Ali (Co-Advisor)
Abstract
With the rapid advances in microwave semiconductor devices and systems, the demand for implementation of nonlinear transmission lines (NLTLs) is rapidly increased. NLTLs support short pulses and wide band-widths. These networks provide cutoff frequencies over hundreds of GHz and picosecond rise times. Among all of the applications of NLTLs, the most attention has been paid to their application in the generation of high power RF pulses. In this application, a high power rectangular pulse is injected to the line, gradually evolved to an oscillatory pulse while propagating through the network, and finally, in the form of a high power RF pulse, is delivered to the load. NLTLs are the most...
Site-Specific Indoor Propagation Modeling Using Ray Tracing Method for 6g Wireless Communications
, M.Sc. Thesis Sharif University of Technology ; Shishegar, Amir Ahmad (Supervisor)
Abstract
This thesis explores the feasibility of implementing terahertz wireless communication in indoor environments (as suggested in 6G) by modeling the propagation of terahertz band waves. The roughness of indoor surfaces at the terahertz frequencies is investigated through the detailed examination of the electromagnetic fields scattered from these surfaces using the method of moments (MoM). To account for the random roughness of these surfaces, the Monte Carlo method is utilized, generating surfaces with Gaussian statistical distribution, and obtaining the scattered electromagnetic fields using MoM. The final results represent an average of all simulated scenarios. In addition, the study...
Control of car-like (wheeled) multi robots for following and hunting a moving target
, Article Scientia Iranica ; Volume 18, Issue 4 B , August , 2011 , Pages 950-965 ; 10263098 (ISSN) ; Kouhi, H ; Salarieh, H ; Sharif University of Technology
2011
Abstract
The main purpose of this paper is to design a decentralized controller for some car-like (wheeled) multi robots to follow and hunt a moving target. Considering geometric dimensions, mass and moment of inertia, robots are very similar to actual cars in which the outputs of the controller are steering and driving wheel torques. All robots are equipped with range and bearing sensors along with antenna, to communicate radio wave signals. A Kalman filter is implemented to estimate relative position, state variables of the target and state variables of other robots. The controller is designed to carry out the group maneuver of the system, based on the system dynamics analysis of inertial agents,...
Efficient shooting and bouncing ray tracing using decomposition of wavefronts
, Article IET Microwaves, Antennas and Propagation ; Volume 4, Issue 10 , 2010 , Pages 1567-1574 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
A new acceleration technique is presented for shooting and bouncing ray tracing in indoor environments. Tracing just a few rays, the algorithm finds the solid angles around the transmitter that transport electromagnetic power to the receiver. The accuracy is then improved by iteratively increasing the tessellation frequency of the source in the power-transporting solid angles. No rays will be sent through non-power-transporting solid angles, which results in significant reduction of the simulation time. An example of applying the method for studying indoor radio wave propagation is presented and the results are compared with a very high-resolution fully three-dimensional (3D) ray tracing...
Ultra-low power current mode all- MOS ASK demodulator for radio frequency identification applications
, Article IET Circuits, Devices and Systems ; Volume 10, Issue 2 , 2016 , Pages 130-134 ; 1751858X (ISSN) ; Sharifkhani, M ; Jalali, M ; Sharif University of Technology
Institution of Engineering and Technology
2016
Abstract
An ultra-low power amplitude shift keying (ASK) demodulator for radio frequency identification (RFID) tags is presented. On the basis of a fast averaging stage, the proposed ASK-demodulator uses a current domain switching envelope amplifier which yields low-power operation. More importantly, it removes the need for a conventional voltage comparator. Designed and fabricated in a 0.18 μm complementary metal-oxide-semiconductor process on about 3000 μm2 silicon area, the proposed demodulator consumes only 7.5 μA from a magnetically coupled induced power. Operating with a 13.56 MHz carrier frequency, the circuit supports modulation indices from 7 up to 100%. The demodulator may as well be used...
A UHF variable gain amplifier for direct-conversion DVB-H receivers
, Article 2009 IEEE Radio Frequency Integrated Circuits Symposium, RFIC 2009, Boston, MA, 7 June 2009 through 9 June 2009 ; 2009 , Pages 551-554 ; 15292517 (ISSN); 9781424433780 (ISBN) ; Sharif Bakhtiar, M ; Medi, A ; IEEE Microwave Theory and Techniques Society; IEEE Electron Devices Society; IEEE Solid-State Circuits Society ; Sharif University of Technology
2009
Abstract
A CMOS fully differential UHF variable gain amplifier for use in a direct-conversion DVB-H receiver is presented employing input devices with variable aspect ratios. High linearity is achieved by reducing the transconductance of the input transistors for lower gain settings. It is shown that this technique has better linearity and noise performance compared to the conventional methods in which the gain reduction is performed at preceding stages. Implemented in TSMC 0.18-μm CMOS process, the inductorless RF VGA covers a voltage gain ranging from 15.5 dB to -6.5 dB with a maximum IIP3 of +24 dBm. The amplifier achieves a 3-dB bandwidth of 1.4 GHz and a minimum noise figure of 5.8 dB while...
Mobile positioning using enhanced signature database method and error reduction in location grid
, Article Proceedings - 2009 WRI International Conference on Communications and Mobile Computing, CMC 2009, 6 January 2009 through 8 January 2009, Kunming, Yunnan ; Volume 2 , 2009 , Pages 175-179 ; 9780769535012 (ISBN) ; Naderi, A. M ; Sharif University of Technology
2009
Abstract
Today, communication science is advancing very rapidly; one of these advances is mobile location determination which means finding position of a mobile station. There are some methods to location determination; one of these methods is Signal Strength (Power of Arrivals). In this research, Mobile Location Determination using enhanced signature database method in a Location grid will be introduced; several ways for positioning error reduction will also be described. © 2009 IEEE
MIMO PCL in a single frequency network
, Article 2011 Microwaves, Radar and Remote Sensing Symposium, MRRS-2011 - Proceedings, 25 August 2011 through 27 August 2011 ; August , 2011 , Pages 280-283 ; 9781424496440 (ISBN) ; Karbasi, S. M ; Khalaj, B. H ; Nayebi, M. M ; Sharif University of Technology
2011
Abstract
Passive localization using MIMO techniques has attracted much attention recently. In such schemes, using multiple antennas at transmitter and receiver sides provides spatial diversity without need for identifiable transmitters. On the other hand, one of the problems facing such approach arises when transmitters of a single frequency network (SFN) are used as non-cooperative transmitters and resolving the signals of multiple transmitters reflected from multiple targets is not trivial at receiver side. Therefore, in order to obtain the diversity gain of MIMO localization schemes, it is necessary to develop a technique to assign each echo arriving at the receiver to a given transmitter. In this...
A compact all-solid-state self-compressing low-to-high power converting rF pulse generator
, Article IEEE Transactions on Plasma Science ; Volume PP, Issue 99 , 2016 ; 00933813 (ISSN) ; Hashemi, S. M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
In this paper, a novel method for high-repetition-rate high-power radio frequency (RF) pulse generation, which involves only passive solid-state devices and is capable of being used for generating high power microwaves using a low-to-high power converting scheme based on nonlinear self-compression is proposed. The method is also expected to be of low jitter. In the proposed circuit, two high voltage diodes with proper reverse recovery characteristics are used. The simulation results show that the proposed circuit generates RF pulses, with central frequencies up to gigahertz range. By applying a sub-kilowatt power supply, the maximum output power was well over 10 kW. This power can be...
Iterative learning control for the radio frequency subsystems of a free-electron laser
, Article IEEE Transactions on Control Systems Technology ; 2017 ; 10636536 (ISSN) ; Smith, R. S ; Sharif University of Technology
Abstract
In linear particle accelerators used for free-electron lasers, it is often required that the electron bunches experience the same electric field as they pass through the accelerating structures. For radio frequency (RF) pulsed mode machines, like the SwissFEL, this means that the amplitude and phase of the RF pulses feeding the structures through the waveguides should be kept constant over the pulselength. This raises an interesting problem that can be addressed by an iterative learning control (ILC) technique. This method manipulates the input waveforms iteratively, in order to generate flat amplitude and phase pulses at the output of the system. In this paper, we introduce two ILC...
Adaptive control of low-level radio frequency signals based on in-phase and quadrature components
, Article IEEE Transactions on Nuclear Science ; Volume 64, Issue 4 , 2017 , Pages 1023-1028 ; 00189499 (ISSN) ; Smith, R. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
This research work presents a low-level radio frequency (RF) control method based on the in-phase, I , and quadrature, Q , components of the RF signal. The proposed method uses only the main four arithmetic operations, i.e., addition, subtraction, multiplication, and division, which makes this control method suitable for implementation on the field-programmable gate array. The control scheme is adaptive in the sense that it estimates the system response on-the-fly, and therefore, it is robust against changes in the loop phase and/or gain during the operation. © 2017 IEEE
Iterative learning control for the radio frequency subsystems of a Free-Electron laser
, Article IEEE Transactions on Control Systems Technology ; Volume 26, Issue 5 , 2018 , Pages 1567-1577 ; 10636536 (ISSN) ; Smith, R. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
In linear particle accelerators used for free-electron lasers, it is often required that the electron bunches experience the same electric field as they pass through the accelerating structures. For radio frequency (RF) pulsed mode machines, like the SwissFEL, this means that the amplitude and phase of the RF pulses feeding the structures through the waveguides should be kept constant over the pulselength. This raises an interesting problem that can be addressed by an iterative learning control (ILC) technique. This method manipulates the input waveforms iteratively, in order to generate flat amplitude and phase pulses at the output of the system. In this paper, we introduce two ILC...
Nonuniform line generator for high-power RF applications
, Article IEEE Transactions on Plasma Science ; Volume 46, Issue 1 , 2018 , Pages 64-71 ; 00933813 (ISSN) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Line generators were attractive structures for high-power radio frequency (RF) pulse generation for two decades. Due to some disadvantages, there has been little attention to this type of generator for a relatively long time. In this paper, a nonuniform line generator is used which resolves some of the main shortcomings of conventional line generators. The considered generator can generate RF pulses at higher frequencies with considerably higher repetition rates. Furthermore, the implementation of nonuniform line generators is significantly easier than that of their conventional counterparts. Measurement results for three nonuniform line generators are presented. The possibility of...
A new dynamic optimal m2m rf interface setting in relay selection algorithm (dorsa) for iot applications
, Article IEEE Access ; Volume 10 , 2022 , Pages 5327-5342 ; 21693536 (ISSN) ; Hemmatyar, A. M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Machine-to-Machine (M2M) communication is an important type of communication in the Internet-of-Things (IoT). How to send data in these high-density communications using relay selection can help improve the performance of this type of communication in various applications. In addition, the possibility of simultaneous use of different Radio Frequency (RF) interfaces helps to use the spectrum more efficiently. In this work, we try to further use machine communication RF equipment and improve the average data rate of networks in some applications such as the IoT, which have their own bandwidth requirements. Therefore, we provide an optimization algorithm for relay selection as well as the...
Radio-wave Propagation Modeling Using Statistical Models and Ray Tracing for Wide-band Wireless Telecommunications
, Ph.D. Dissertation Sharif University of Technology ; Farzaneh, Forouhar (Supervisor) ; Shishegar, Amir Ahmad (Co-Advisor)
Abstract
Ever-increaing demand for wireless communication systems impels an efficient system planning before the system deployment. The very first step of the planning is radio-wave channel modeling. Generally, all propagation models can be categorized in three types of models: Emprical models, semi-emprical models and deterministic models. The statistical and semi-emprical models can give a quite prompt signal level prediction over the vast propagation area using few computations. In the recent wireless services which wider bandwidth is required, only the signal level prediction cannot give a proper perspective of design and planning. The parameters such as the power-delay profile, rms delay spread;...